Compressors comprise a housing with a housing insert, which can be inserted, serves as a stator and is also called a return stage. Each rotor of the compressor is usually assigned a return stage. With regard to use at low temperatures or in the case of great temperature differences, return stages can have a three-point mounting. Said three-point mounting is necessary, in order that the components can expand thermally, without causing pressure between the housing and the return stage or other components which are attached in the interior of the housing. The adjusting or centering of a return stage takes place via three mounting points, on which the return stage is mounted. In practice, the radial orientation or adjustment of the return stage via said three points is difficult, however, since the return stage can lie eccentrically with respect to the housing as a result of tolerances. In the case of eccentric mounting of this type, the gap between the return stage and a shaft of the compressor is reduced on one side, with the result that rubbing of the rotor might occur in the worst case. In practice, the radial guidance of the housing insert (return stage) is therefore adapted in a complicated manner if the internal diameter and external diameter are not concentric.
This operation is shown diagrammatically in FIG. 1. FIG. 1 shows a housing 1 of a conventional turbomachine and a housing insert 2 which is received spaced apart therein. The measurement and adaptation are complicated, since a gap s which is measured between the housing 1 and the housing insert 2 has to be transferred to a gap t at the lowest point of the housing insert. It has to be ensured here that the internal diameter lies coaxially with respect to the housing middle or with respect to the bearing center.
The vertical orientation of the housing insert 2 takes place by way of two adjusting pieces in the joint region. The adjusting pieces which are shown using dashed lines in FIG. 1 are connected to the housing insert 2 and are adapted; a gap is situated to the side thereof. A further adjusting piece which assumes the horizontal guidance is used on the underside. In order to adapt said adjusting piece laterally, it is necessary to remove the housing insert 2 from the turbomachine, possibly several times. A gap is situated below the said adjusting piece, in order to make a vertical movement of the housing insert 2 possible.